Intravascular guidewire

ABSTRACT

A guidewire for use in a medical procedure includes an elongate guide member dimensioned for insertion within a body vessel of a subject. The guide member defines a longitudinal axis and has trailing and leading end segments. The leading end segment has a reduced cross-sectional dimension relative to a cross-sectional dimension of the trailing end segment. The leading end segment includes a first core element comprising a first material and a second core element comprising a second material different from the first material and being forward of the first core element. The first material of the first core element has greater rigidity than the rigidity of the second material of the second core element, to thereby facilitate advancement of, and application of torque to, the leading end segment while minimizing deformation. The first material of the first core element may comprise a nickel-cobalt-chromium alloy or, alternatively, stainless steel. The second material of the second core element comprises a nickel-titanium or an alloy thereof.

This application is a continuation of U.S. patent application Ser. No.13/407,182, which was filed on Feb. 28, 2012 and is entitled,“INTRAVASCULAR GUIDEWIRE,” the entire content of which is incorporatedby reference herein.

BACKGROUND 1. Technical Field

The present disclosure generally relates to intravascular devices, and,in particular, relates to an intravascular guidewire for assisting inplacement of an intravascular device within, e.g., the neurovascularspace, for facilitating diagnostic and/or therapeutic neurovascularprocedures.

2. Description of Related Art

The effectiveness of an intravascular guidewire in advancing throughtortuous vasculature without undesired deformation or kinking isdependent upon a number of factors and design considerations. Thesefactors include, inter-alia, the material(s) of fabrication of theguidewire, guidewire dimensions and intended use. Generally, a balancemust be achieved to provide the required torsional, lateral, tensileand/or column strengths to enable easy and precise manipulation andsteerability in the tortuous vasculature. Guidewires for neurovascularintravascular procedures face additional challenges due to therelatively small diameter required to navigate through the narrow andremote locations of the neurovasculature space.

SUMMARY

Accordingly, the present disclosure is directed to a guidewire capableof accessing distal reaches of the vasculature, including theneurovasculature, while exhibiting sufficient torsional and lateralstiffness to enable steering of the guidewire through these tortuousregions. What is also desired is a guidewire having a distal end withimproved tensile and torsional integrity, yet with the capability toreadily bend in any direction.

In accordance with one embodiment of the present disclosure, a guidewirefor use in a medical procedure includes an elongate guide memberdimensioned for insertion within a body vessel of a subject. The guidemember defines a longitudinal axis and has trailing and leading endsegments. The leading end segment has a reduced cross-sectionaldimension relative to a cross-sectional dimension of the trailing endsegment. The leading end segment includes a first core elementcomprising a first material and a second core element comprising asecond material different from the first material and being forward ofthe first core element. The first material of the first core element hasgreater rigidity than the rigidity of the second material of the secondcore element, to thereby facilitate advancement of, and application oftorque to, the leading end segment while minimizing deformation. Thefirst material of the first core element may comprise anickel-cobalt-chromium alloy or, alternatively, stainless steel. Thesecond material of the second core element may comprise nickel-titaniumor an alloy thereof. The first core element may be directly bonded tothe second core element through, e.g., a welding process, which may bedevoid of any filler material.

A coil member may be coaxially mounted about the guide member anddimensioned to longitudinally extend to at least partially encompass thefirst and second core elements. The coil member may include a first coilsegment and a second coil segment forward of the first coil segment. Thefirst coil segment may comprise a first coil material and the secondcoil segment may comprise a second coil material different from thefirst coil material. The first coil segment may have a first torsionalstrength and the second coil segment may have a second torsionalstrength greater than the first torsional strength. The second coilsegment may be required to assume a greater torsional load to compensatefor, e.g., a reduced cross sectional dimension adjacent the tip of theguide member.

The leading end segment may include at least two tapered segmentsobliquely arranged with respect to the longitudinal axis. In oneembodiment, the leading end segment includes, from leading to trailing:a remote segment; a first tapered segment extending from the firstremote segment and coterminous therewith; a first generally annularsegment extending from the first tapered segment and coterminoustherewith; a second tapered segment extending from the second generallyannular segment and coterminous therewith; and a second generallyannular segment extending from the second tapered segment andcoterminous therewith. In embodiments, the first core element isconnected to the second core element within the second generally annularsegment or may be connected within the third generally annular segment.

A sleeve may be mounted over at least a major portion of the leading endsegment. The sleeve may comprise polyurethane and tungsten material. Thesleeve also may define an arcuate distal tip.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will be readily appreciated byreference to the drawings wherein:

FIG. 1 is a perspective view of a guidewire and catheter in use within atortuous region of the vasculature of a patient in accordance with theprinciples of the present disclosure;

FIG. 2 is a perspective view with parts separated of the guidewire ofFIG. 1 illustrating the guide member, support springs and outer sheath;

FIG. 3 is a side cross-sectional view of the leading end segment of theguide member of the guidewire of FIGS. 1 and 2;

FIG. 4 is a cross-sectional view of the guide member of the guidewiretaken along the lines 4-4 of FIG. 3;

FIG. 5 is a cross-sectional view of the guide member of the guidewiretaken along the lines 5-5 of FIG. 3; and

FIG. 6 is a cross-sectional view of the guide member of the guidewiretaken along the lines 6-6 of FIG. 3.

DESCRIPTION

In the following description, the terms “proximal” and “distal” as usedherein refer to the relative position of the guidewire in a lumen. The“proximal” or “trailing” end of the guidewire is the guidewire segmentextending outside the body closest to the clinician. The “distal” or“leading” end of the guidewire is the guidewire segment placed farthestinto a body lumen from the entrance site.

The guidewire of the present disclosure has particular application in aneurovascular procedure, but may be used in any interventional,diagnostic, and/or therapeutic procedure including coronary vascular,peripheral vascular, and gastro-intestinal applications in addition to aneurovascular application.

In the figures below, the full length of the guidewire is not shown. Thelength of the guidewire can vary depending on the type of interventionalprocedure, though typically it ranges in length from 30 to 400centimeters (cm). Common lengths of guidewires for coronary, peripheraland neurovascular interventions may range from 170 to 300 cm in length.These lengths permit the use of standardized rapid exchange orover-the-wire catheter systems. The length of the shaped distal end alsomay vary, for example, from about 5 to about 80 cm in length.

In accordance with one application of the present disclosure, themaximum outer diameter of the guidewire ranges from about 0.008 inchesto about 0.018 inches. These diameters are standard for guidewires used,e.g., in a neurovascular procedure. Other diameters are contemplated forcardiovascular, peripheral vascular, and gastrointestinal applications.The diameter of the guidewire may remain relatively constant over amajor portion of the length of the guidewire; however, the leading ordistal end incorporates a generally tapered or narrowed configuration topermit flexure while navigating the tortuous vasculature.

The various embodiments of the disclosure will now be described inconnection with the drawing figures. It should be understood that forpurposes of better describing the disclosure, the drawings may not be toscale. Further, some of the figures include enlarged or distortedportions for the purpose of showing features that would not otherwise beapparent.

Referring now to FIG. 1, a tortuous vasculature such as within theneurovascular space “n” is illustrated. For illustrative purposes, atortuous path or a tortuous region within, e.g., the neurovascular space“n”, includes large vasculature “v1” and smaller branch vessels “v2”which branch or extend from more proximal vessels at various angles,including up to 90 degrees or even greater than 90 degrees.

In FIG. 1, guidewire 10 of the present disclosure is illustrated asbeing positioned within a conventional access or microcatheter 100. Suchmicrocatheters are known in the art. One suitable microcatheter is thereinforced microcatheter disclosed in commonly assigned U.S. Pat. No.7,507,229 to Hewitt et al., the entire contents of which areincorporated by reference herein. In general, microcatheter 100 includeshandle 102 and hollow catheter member 104 extending from the handle 102.Microcatheter 100 defines a longitudinal opening extending at leastthrough catheter member 104 for passage or reception of guidewire 10.

Guidewire 10 includes actuator 12 and guide member 14 extending from theactuator 12. Actuator 12 may incorporate various features includeshandles, slides or the like, to facilitate handling and/or movement ofguide member 14. For example, actuator 12 may be used to translateand/or rotate guide member 14 during placement within the vasculature.

Referring now to FIG. 2, guide member 14 of guidewire 10 is illustratedand will be discussed in greater detail. Guide member 14 is dimensionedfor insertion within the vasculature. Guide member 14 defineslongitudinal axis “k” and has proximal or trailing end segment 16 anddistal or leading end segment 18 forward of the trailing end segment 16.In FIG. 2, a major longitudinal portion of proximal end segment 16 isremoved for ease of illustration. Trailing end segment 16 may begenerally circular in cross-section with a length ranging from about 20cms. to about 240 cms. Trailing end segment 16 may have a constantcross-sectional dimension or diameter along its length.

With reference now to FIGS. 2-3, leading end segment 18 of guide member14 is the working end or tip of the guidewire 10 and defines a reducedcross-sectional dimension relative to the cross-sectional dimension ofproximal end segment 16. The overall length “L” (FIG. 2) of leading endsegment 18 may range from about 20 cms to about 60 cms depending on themaximum diameter (e.g., the diameter of proximal end segment 16) and theoverall length of guidewire 10. Leading end segment 18 may include anumber of alternating tapered and annular segments which generallyincrease in cross-sectional dimension or diameter from the extremeremote or distal end toward the proximal end, i.e., toward proximal endsegment 16. In the embodiment of FIGS. 2-3, leading end segment 18includes distal remote segment 20, first tapered segment 22 extendingfrom the remote segment 20 and coterminous therewith, first generallyannular segment 24 extending from the first tapered segment 22 andcoterminous therewith, second tapered segment 26 extending from thefirst generally annular segment 24 and coterminous therewith, and secondgenerally annular segment 28 extending from the second tapered segment26 and being coterminous therewith. Leading end segment 18 may furtherinclude third tapered segment 30 extending contiguously from secondannular segment 28 and third annular segment 32 which is coterminouswith the third tapered segment 30. As a further alternative, leading endsegment 18 may also include fourth tapered segment 34 extending fromthird annular segment 32 to leading end segment 16. First, second andthird annular segments 24, 28, 32 may define circular cross-sectionswith various diameters as depicted in the cross-sectional views of FIGS.4, 5 and 6, respectively. Suitable diameters of each of annular firstsecond and third annular segments 24, 28, 32 for specific guidewiresizes will be provided hereinbelow. Tapered segments 22, 26, 30 and 34are in oblique relation to the longitudinal axis “k”. Tapered segments22, 26 may define an angle relative to longitudinal axis “k” rangingfrom about 5 degrees to about 30 degrees. Tapered segments 30, 34 maydefine a greater angle relative to longitudinal axis “k”, e.g., rangingfrom about 20 degrees to about 70 degrees.

Remote segment 20 may define various configurations. In the embodimentof FIGS. 2-3, remote segment 20 is a flattened, planar or ribbon tip.However, remote segment 20 may define alternative cross-sectional shapesincluding circular, oval or the like. As a further alternative, remotesegment 20 may be heat set into a variety of configurations including alinear arrangement. In one embodiment, remote segment 20 is heat set tomaintain, e.g., a non-linear configuration such as a curve, bysubjecting the remote segment 20 to heat at about 500° C. to about 525°C. for a duration of time ranging from about 30 seconds to about 2minutes. Remote segment 20 may also be provided with a bent “j-hook” asis known in the art, or, may be bent into a “j-hook” design by theclinician prior to the interventional procedure.

With particular reference to FIG. 3, in conjunction with FIG. 2, inaccordance with an embodiment of the disclosure, leading end segment 18is fabricated from at least two core elements having different corematerials with different mechanical properties. For example, first coreelement 36 encompasses at least a section of second annular segment 28and extends proximally toward proximal or trailing end segment 16 ofguidewire 10, and may encompass the entirety of the trailing end segment16. Second core element 38 (identified by the different cross-hatchingin FIG. 3) is distal or forward of first core element 36 and mayencompass the remaining distal section of second annular segment 28,second tapered segment 26, first annular segment 24, first taperedsegment 22 and remote segment 20. As will be discussed in detailhereinbelow, first core element 36 and second core element 38 are joinedat bond location 40.

Second core element 38 may comprise a shape memory or superelastic alloyor polymer. One suitable shape memory alloy (SMA) or superelastic metalis Nitinol (NiTi), a nickel/titanium alloy, which is commerciallyavailable in various diameters or sizes. Superelastic alloys such asNiTi are relatively flexible capable of effectively tracking tortuousvasculature encountered while exhibiting advantageous restorationcapabilities. Shape memory or superelastic metal or polymer such as NiTimay also be suitable for applications in which it is desired thatleading end segment 18 have a pre-determined curvature. Shape memoryalloys including NiTi can be heat set into a desired shape, straightenedfor delivery to a site, and then released to resume the heat-set shape.Other materials for second core element 38 may include an alloyconsisting of Nickel, Titanium, and Cobalt commercially available fromSAES Smart Materials, Inc, of New Hartford, N.Y.

First core element 36 is preferably fabricated from a more rigidmaterial having a greater elastic modulus, torsional and/or lateralrigidity than the material of second core element 38. In one embodiment,first core element 36 is fabricated from MP35N, a nickel-cobalt alloy.MP35N is a cold worked, age hardenable nickel-cobalt base alloy having acombination of strength, toughness, durability and corrosion resistance.A typical composition of MP35N is 35% Nickel (Ni), 35% Cobalt (CO), 20%Chromium (Cr) and 10% Molybdenum (MO). Wire fabricated from MP35N iscommercially available in various diameter sizes from, e.g., Fort WayneMetals of Fort Wayne, Ind. The more rigid first core element 36 enhancespushability through the vasculature and torque transmission as will bediscussed. Other suitable materials for first core element 36 includestainless steel, titanium and alloys thereof, and the Nickel TitaniumCobalt alloy identified hereinabove. The properties of these materialsmay be altered through the use of additive materials, manufacturingprocesses or the like to provide the required lateral strength andstiffness to realize the desired characteristics of first core element36 discussed hereinabove.

First core element 36 may be bonded to second core element 38 at bondinglocation 40 within second annular segment 28 through various meansincluding bonding, welding, adhesives or the like. In one embodiment,first core element 36 is secured to second core element 38 through awelding process such as a laser or radio frequency (RF) welding process.The welding process contemplated is devoid of filler or bondingmaterials, thereby providing a direct connection or mating of theelements of first and second core elements 36, 38 during application ofheat. The ends of each of first and second core elements 36, 38 to bejoined may be subjected to an acid wash to remove impurities, and/oredges prior to welding of the components.

The provision of first and second core elements 36, 38 of differentmaterials having different elastic modulus, rigidities and/or torsionalstrengths within leading end segment 18, in combination with thedimensioning of the components of the leading end segment 18, providessignificant benefits with respect to pushability, lateral strength,torque transfer and flexibility of the guidewire 10. For example, in oneembodiment, second core element 38 encompasses about 10% to about 20% ofthe overall length of leading end segment 18. In embodiments, secondcore element 38 may extend from remote end 20 a distance “m” (FIG. 3)ranging from about 10 cm to about 20 cm. This localization or provisionof the less rigid second core element 38 at the remote end of leadingend segment 18 (and/or the relatively increased length of the more rigidfirst core element 36 within the leading end segment 18) increasespushability of guide member 12 within the tortuous vasculature, improvestorque transmission and minimizes distal deformation while alsoproviding sufficient flexibility to accommodate the turns of thevasculature within the neurovascular space. The respective lengths offirst and second core elements 36, 38 for various guidewire sizes areoutlined in the Table hereinbelow.

As mentioned hereinabove, in the embodiment depicted in FIGS. 2 and 3,first and second core elements 36, 38 are joined at location 40 withinsecond annular segment 28. It is envisioned that the juncture locationmay be anywhere along leading end segment 18, including, e.g., alongsecond tapered segment 26, third tapered segment 30 or third annularsegment 32, e.g., at location 41, or arranged to be bonded within firstannular segment 24, e.g., at location 43.

With continued reference to FIGS. 2 and 3, leading end segment 18further includes at least one coil coaxially mounted about at least aportion of the leading end segment 18, and outer sheath 42. Inembodiments, leading end segment 18 includes two coils, namely, first orproximal coil segment 44 and second or distal coil segment 46 forward ofthe proximal coil segment 44. Proximal coil segment 44 may be fabricatedfrom a number of materials including MP35N discussed hereinabove.Proximal coil segment 44 may be dimensioned to extend to encompasssecond annular segment 28 and a portion of second tapered segment 26.The diameter of the wire of proximal coil segment 44 may range fromabout 0.0009 inches to about 0.0025 inches, and, in one embodiment, isabout 0.0012 inches. Proximal coil segment 44 may also have arectangular or flattened cross-section.

Distal coil segment 46 extends from proximal coil segment 44 andencompasses the remainder of leading end segment 18 of guide member 14.Distal coil segment 46 may be fabricated from a number of materials. Inone embodiment, distal coil segment 46 is fabricated from thecommercially available radiopaque Biomed material sourced byJohnson-Matthey of London, England, and is offered in 3 grades, namely,grade 1400 including 86% Palladium (Pd), 14% Rhenium(Re), grade 1000including 90% Pd, 10% Re and grade 500 including 95% Pd, 5% Re. The wireof distal coil segment 46 has a diameter greater than the wire ofproximal coil segment 44. In one embodiment, the diameter of distal coilsegment 46 ranges from about 0.0012 inches to about 0.0025 inches, andmay be about 0.0015 inches. Distal coil segment 46 may also have arectangular or flattened cross-section. The radiopacity of distal coilsegment 46 may assist in placement of leading end segment 18 within thevasculature through the use of imaging means, e.g., fluoroscopicallyduring the interventional procedure.

Proximal coil segment 44 and distal coil segment 46 may provide lateraland/or torsional support to leading end segment 18. In one embodiment,the lateral strength (or resistance to bending) of distal coil segment46 is less than the lateral strength of proximal coil segment 44 topermit flexing of second core element 38 of leading end segment 18. Theouter diameters of proximal and distal coil segments 44, 46 mayapproximate each other and may be substantially equivalent to thediameter of third annular segment 32 to provide a smooth transition. Theconfigurations of proximal and distal coil segments 44, 46 may bechanged to provide varied properties if desired. In an embodiment,proximal and distal coil segments 44, 46 may be wound or otherwisedisposed about leading end segment 18 in differing or oppositedirections. In embodiments, adjacent turns of the coils of each ofproximal and distal coil segments 44, 46 are in contacting relation(i.e., they are devoid of spacing between the adjacent coil turns). Inone embodiment, proximal and distal coil segments 44, 46 may be joinedat their interface. In addition, proximal and distal coil segments 44,46 may be attached to leading end segment 18 of guide member 14 alongvarious locations. Attachment may be effected though the use ofadhesives, welding, soldering or the like. Distal coil segment 46 may beoperatively connected or secured to remote end 20 of leading end segment18 through a soldering process or with the use of an adhesive such as anepoxy, cyanoacrylate adhesive or an ultraviolet (UV) light curableadhesive. The soldering or adhesive element is represented schematicallyas element 48 in FIG. 3.

Outer sheath 42 encloses leading end segment 18 and proximal and distalcoil segments 44, 46. Outer sheath 42 may be fabricated from anysuitable material. In one embodiment, outer sheath 42 is a polyurethanesleeve which may or may not be loaded with tungsten, e.g., in microbeadform. If loaded with tungsten, outer sheath 42 provides an additionalelement of radiopacity to leading end segment 18 of guide member 14.Outer sheath 42 may be thermoformed over leading end segment 18 andproximal and distal coil segments 44, 46 through conventional thermoformtechniques. Outer sheath 42 defines an atraumatic arcuate leading endsurface 50 to minimize the potential of trauma or abrasion of the vesselwalls. In one embodiment, the diameter of outer sheath 42 is less thanthe diameter of proximal or trailing end segment 16 of guide member 14to provide a smooth transition between the components.

The Table provided below identifies ranges of dimensions of thecomponents of the leading end segment 18 for various guidewire sizes inaccordance with the principles of the present disclosure. In the Table,D is represented as a percentage (%) of the diameter of the trailing endsegment 16 and L represents the specific length of the component. Forexample, the diameter of first annular segment 24 may range from about10% to about 30% of the diameter of trailing end segment 16 and have alength ranging from about 2 cms. to about 10 cms. All ranges areapproximate. Preferred dimensions for the specific guidewire sizes maybe at the midpoint of the specified ranges. Variations of thesedimensions are envisioned. The first core element 36 is fabricated fromMP35N and the second core element 38 is fabricated from NiTi. As noted,the overall length of first core element 36 may range from about 10 cms.to about 40 cms. and the overall length of second core element 38 mayrange from about 20 cms. to about 290 cms.

TABLE 1^(st) Annular 2nd Annular 3^(rd) Annular First Core Second CoreSegment Segment Segment Element Element 24 28 32 36 38 D (%) 10-30%25-50% 50-90% L (cms.) 2-10 cms. 5-30 cms. 10-30 cms. 10-40 cms. 20-290cms.

It is further envisioned that a lubricious coating may be disposed overcomponents of guide member 14 including outer sheath 42. Suitablelubricious coatings include hydrophilic materials such aspolyvinylpyrrolidone (PVP), polyethylene oxide, polyethylene glycol,cellulosic polymers, and hydrophilic maleic anhydride, or hydrophobicmaterials such as silicone, PTFE, or FEP. These coatings are typicallyapplied by dip coating or spray methods, and heat curing may be used.For example, cure temperatures up to about 70 degrees C. are used forsilicone coatings, and several hundred degrees may be required for PTFEcoatings. In addition to the lubricious coating, bioactive coatings maybe applied over all or part of the guidewire. Such coatings also mayincorporate materials such as heparin, hirudin and its analogs, or otherdrugs. These coatings typically are applied by dip coating. Bioactivecoatings are desirable to prevent blood clotting or for delivery ofdrugs to a specific site.

The above description and the drawings are provided for the purpose ofdescribing embodiments of the present disclosure and are not intended tolimit the scope of the disclosure in any way. It will be apparent tothose skilled in the art that various modifications and variations canbe made without departing from the spirit or scope of the disclosure.Thus, it is intended that the present disclosure cover the modificationsand variations of this disclosure provided they come within the scope ofthe appended claims and their equivalents.

1-20. (canceled)
 21. A guidewire comprising: an elongate guide memberdimensioned for insertion within a body vessel of a subject, the guidemember comprising a proximal segment and a distal segment, the distalsegment having a reduced cross-sectional dimension relative to across-sectional dimension of the proximal segment, the distal segmentincluding: a first core element comprising a first material; and asecond core element comprising a second material different from thefirst material, the second core element being distal to the first coreelement, wherein a proximal end of the second core element is directlywelded to a distal end of the first core element such that the secondmaterial of the second core element is directly bonded to the firstmaterial of the first core element, the first material of the first coreelement having greater rigidity than the rigidity of the second materialof the second core element.
 22. The guidewire of claim 21, wherein thefirst material of the first core element comprises anickel-cobalt-chromium alloy.
 23. The guidewire of claim 21, wherein thefirst material of the first core element comprises stainless steel. 24.The guidewire of claim 23, wherein the second material of the secondcore element comprises an alloy including nickel and titanium.
 25. Theguidewire of claim 21, wherein the distal segment is devoid of anyfiller material between the proximal end of the second core element andthe distal end of the first core element.
 26. The guidewire of claim 21,further comprising a coil member coaxially mounted about the guidemember and dimensioned to longitudinally extend to at least partiallyencompass and engage with each of the first and second core elements.27. The guidewire of claim 26, wherein the coil member includes a firstcoil segment and a second coil segment forward of the first coilsegment, the first and second coil segments comprising differentmaterials.
 28. The guidewire of claim 26, wherein the first coil segmenthas a first torsional strength and the second coil segment has a secondtorsional strength greater than the first torsional strength.
 29. Theguidewire of claim 21, wherein the distal segment includes at least twotapered segments that taper in outer diameter.
 30. The guidewire ofclaim 29, wherein the distal segment includes, from distal to proximal:a first remote segment; a first tapered segment extending from the firstremote segment; a first generally annular segment extending from thefirst tapered segment; a second tapered segment extending from the firstgenerally annular segment; and a second generally annular segmentextending from the second tapered segment.
 31. The guidewire of claim30, wherein the first core element is directly welded to the second coreelement within the second generally annular segment.
 32. The guidewireof claim 30, wherein the distal segment further comprises: a thirdtapered segment extending from the second generally annular segment; anda third generally annular segment that extends from a third taperedsegment, wherein the first core element is directly welded to the secondcore element within the third generally annular segment.
 33. Theguidewire of claim 30, wherein the remote segment defines one of apolygonal cross-section or an annular cross-section.
 34. The guidewireof claim 30, wherein the remote segment is heat set into a predeterminedarcuate configuration.
 35. The guidewire of claim 21, further comprisinga sleeve mounted over at least a major portion of the distal segment.36. The guidewire of claim 35, wherein the sleeve comprises polyurethaneand tungsten material.
 37. The guidewire of claim 21, wherein the firstand second core elements do not overlap in an axial direction, the axialdirection extending parallel to a longitudinal axis of the elongateguide member.
 38. A guidewire comprising: an elongate guide memberdimensioned for insertion within a body vessel of a subject, the guidemember comprising a proximal segment and a distal segment, the distalsegment having a reduced cross-sectional dimension relative to across-sectional dimension of the proximal segment, the distal segmentincluding: a first core element comprising a first material; and asecond core element comprising a second material, the first material ofthe first core element having greater rigidity than a rigidity of thesecond material of the second core element, wherein the second coreelement is distal to the first core element, wherein a proximal-most endof the second core element is directly bonded to a distal-most end ofthe first core element such that the second material of the second coreelement is directly bonded to the first material of the first coreelement.
 39. The guidewire of claim 38, wherein the first material ofthe first core element comprises a nickel-cobalt-chromium alloy orstainless steel, and the second material of the second core elementcomprises an alloy including nickel and titanium.
 40. The guidewire ofclaim 38, wherein the proximal-most end of the second core element isbonded to the distal-most end of the first core element through awelding process, the welding process devoid of any filler material. 41.The guidewire of claim 38, further comprising a coil member coaxiallymounted about the guide member and dimensioned to longitudinally extendto at least partially encompass and engage with each of the first andsecond core elements.
 42. The guidewire of claim 38, wherein the firstcore element is directly welded to the second core element within anannular segment of the guide member.